1. Field of the Invention
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2. The Prior Art
The present invention relates to a multi-part piston for an internal combustion engine, having an upper piston part that has a piston crown, and a lower piston part, whereby the lower piston part has pin boss supports and pin bosses connected with them, whereby the upper piston part and the lower piston part each have an inner and an outer support element, which elements delimit an outer circumferential cooling channel. The present invention furthermore relates to a method for the production of such a piston.
A multi-part piston is disclosed, for example, in EP 1 222 364 B1. This piston has an outer circumferential cooling channel and an inner cooling chamber whose cooling chamber bottom is provided with an opening. This opening serves to allow cooling oil to flow away out of the inner cooling chamber in the direction of the piston crown, in order to lubricate the piston pin and to intensify the cooling effect by means of effective cooling oil circulation. In order to achieve this goal, the opening in the cooling chamber bottom is not allowed to be chosen to be too large, because then, the cooling oil would no longer flow away in metered manner, and effective cooling oil circulation would thereby be impaired. This means that the cooling chamber bottom is configured essentially as a relatively wide and thin circumferential ring land that extends approximately in the radial direction, in the upper region of the lower piston part. However, such a structure is difficult to produce. In the case of a forged lower piston part, in particular, there is the additional problem that when using a forging method, only a very thick and heavy cooling chamber bottom can be produced, due to forging tolerances and production restrictions.